1. Field of the Invention
The present invention relates to a road situation perceiving system for perceiving snow, ice, a person, an animal and other impediments and obstacles existing on a road ahead of a subject vehicle without relying on a driver's visual judgment.
2. Description of the Related Art
A technique is known from a Japanese Patent Application Laid-open No. 89298/85, which judges whether it is possible for a subject vehicle to pass through a curve ahead of the subject vehicle in a traveling direction at the current speed by estimating a radius of curvature of the curve based on map data obtained by a navigation system. According to the known technique an alarm is given to a driver when it is determined that it is impossible for the subject vehicle to pass through the curve at the current speed.
In the above known technique, it is possible to perceive the condition of the curve of the road ahead at a position short of the curve to perform a countermeasure such as a speed reduction. However, the above known technique has a limitation in that it is impossible to perceive an iced condition of a road ahead of the subject vehicle or a potentially hazardous situation such as an existence of a walker on a road. Correspondingly, the known technique does not alleviate a burden on the driver in a poor-visibility condition, particularly, in the night or in a fog, of having to perceive such road conditions and obstacles.